#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

int Fib(int n)
{
	int a = 1;
	int b = 1;
	int c = 1;
	while(n >= 3)
	{
		c = a + b;
		a = b;
		b = c;
		n--;
	}
	return c;
}


int main()

 {
	int n = 0;
	scanf("%d", &n);
	int r = Fib(n);
	printf("%d", r);


  return 0;
 }
